1. Field of the Invention
This invention relates to segmented N-alkyl polyurethane amides, to a process for their production and to their use for the production of moldings, films and fibers, particularly for use in the medical field.
2. Brief Description of the Prior Art
Polyurethanes are often used for the production of moldings, films and fibers, particularly those intended for the medical applications. These polyurethanes are distinguished by excellent mechanical properties and by relatively favorable compatibility with the body. However, a disadvantage of the polyurethanes in question is that during thermoplastic processing at temperatures above 200.degree. C., they are split back into the starting polyols and the isocyanates show inadequate hydrolytic stability (see, for example, S. Gogolewski in Colloid Polymer Science No. 267, 1989, 757 to 785 or J. H. Saunders in Rubber Chem. Technol. 32, 1959, 337 et seq. or H. Shintani and A. Nakamura in Journal of Analytica Toxicology 13, 1989, 354 to 357). Accordingly, there was a need to provide heat-stable and hydrolysis-stable materials for the production of moldings, films and fibers, particularly for use in the medical field, which materials, at the same time would show the desired level of mechanical properties.
It has now been found that N-alkyl polyurethane amides corresponding to formula (I) satisfy these requirements.